Tar

Tar causes cancer of the lungs, mouth and throat. It coats the inside of the lungs, including the alveoli, causing coughing. It damages the alveoli, making it more difficult for gas exchange to happen.

Smoke

Cells in the lining of the trachea, bronchi and bronchioles produce sticky mucus. This traps dirt and microbes. Cells with tiny hair-like parts, called cilia then move the mucus out of the lungs.

However, hot smoke and tar from smoking damages the cilia. As a result of this, smokers cough to move the mucus and are more likely to get bronchitis.

Nicotine

Nicotine is addictive. It causes a smoker to want more cigarettes. Nicotine also increases the heart rate and blood pressure, and makes blood vessels narrower than normal. This can lead to heart disease.

Carbon monoxide

Carbon monoxide is a gas that takes the place of oxygen in red blood cells. This reduces the amount of oxygen that the blood can carry. It means that the circulatory system has to work harder, causing heart disease.